The invention relates to solid-bowl screw centrifuges.
It is known from the prior art to provide disk arrangements in solid-bowl screw centrifuges.
U.S. Patent Document U.S. Pat. No. 5,310,399 shows disks which are arranged on the screw body, specifically between several spirals of the screw.
A similar construction is known from German Patent Document DE 26 17 692. Also, in this multi-stage decanter arrangement, the disks are arranged on the screw.
In addition, there are constructions in which a type of disk drum is connected behind the actual decanter drum (see, for example, IT 496 031 or SU 385 629).
Additional known combinations of solid-bowl screw centrifuges with disk inserts are known from International Patent Document WO 98/45045, French Patent Document 1 449 064, French Patent Document 2 532 189 and British Patent Document GB 998 669.
In British Patent Document GB 998 669, a type of a complete separator is connected on the output side of the decanter as a constructional unit. As a result, the after clarification of the product preclarified in the decanter basically takes place in a completely separate series connection of the decanter and the separator.
In the separator with the stack of disks, the concentrate is discharged on a larger diameter of the nozzles and the clarified phase is discharged in the center. Outside the stack of disks, a solid matter space is constructed which is bounded on both sides by conical walls. The outside diameter of this separator, for example, in SU 385 629 or GB 998 669, is situated on a larger radius than the outside diameter of the decanter.
The initially mentioned decanter constructions with integrated disk stacks are distinguished in that the disk stacks are each mounted on the screw bodies and thus rotate at a differential rotational speed with respect to the drum casing. This necessarily results in disturbing gaps. Furthermore, no optimal utilization of the space can be accomplished.
From International Patent Document WO 99/52641 (as well as parallel U.S. Patent Document U.S. Pat. No. 6,030,332), it is known to mount a disk stack directly upstream of the liquid outlet, so that it is arranged on the drum cover. However, in this case, it is problematic that the disk stack essentially fills out the cylindrical area of the centrifuge, so that, differently than in British Patent Document GB-A-998669, a separator is not connected to the output side of a complete decanter, which first develops its effect. A similar construction as that of U.S. Patent Document U.S. Pat. No. 6,030,322 is illustrated in German Patent Document DE 1 482 721.
An aspect of the present invention is a centrifuge that has a discharge of concentrate take place from an area of a disk stack toward a drum casing.
The present invention is a solid-bowl screw centrifuge that includes a centrifugal drum. The drum has a drum casing and a screw with a screw body that is surrounded by a screw blade. The screw blade forms at least one screw spiral with a conveying path constructed between the at least one screw spiral for transporting material to be centrifuged. The centrifuge also includes an inlet into the centrifugal drum, at least one solid matter discharge and at least one liquid outlet. The centrifuge also includes a drum chamber that is axially closed by a drum cover having essentially a conical shape. Further included is a disk stack having at least one conical disk, and the disk stack is mounted to the drum cover directly upstream of the liquid outlet. At least a portion of the disk stack is arranged in a cylindrical section of the drum chamber that has an essentially constant diameter. A screw disk is arranged on the screw body between the drum cover and a first screw spiral of the at least one screw spiral. The screw disk has an interior section and a conical exterior section.
The conical section of the screw disk as well as the conical drum cover constructed opposite the conical section of the screw disk thereby form a solid matter or concentrate collecting space which is conically tapered twice. That permits a draining of the concentrate toward the drum casing without requiring a joining of a separately constructed separator connected to the output side of the decanter. For at least this purpose, the disk stack is arranged in a cylindrical section of the drum chamber with an essentially constant diameter and the disk stack is mounted directly upstream of the liquid outlet, while resting on the drum cover and/or being arranged on the latter.
Since the stack of disks rests directly on the drum cover or is fastened thereto, it no longer rotates at a differential rotational speed with respect to the drum casing but rotates together with it.
In contrast to disk inserts on the screw, a disk insert or stack of disks connected with a liquid-side drum casinggenerally prevents disturbing short-circuit connections from occurring between a clear-phase collecting pipe of the disk stack and a solid matter or concentrate space outside the disk stack. The concentrate space of the disk stack is situated on the outside on the disk stack, in which the diameter of the drum casing can be constructed to be continuous or constant and requires no widening. In this manner, mixtures which are difficult to clarify, for example, mixtures with fine suspended matter, can be separated.
The maximal radial dimension of the screw disk is preferably smaller than the radial dimension of the screw blade. In particular, discharge is achieved by a removal device on the first screw blade which penetrates the screw disk.
The drum cover preferably has an essentially conical construction, which permits a fastening of the preferably preassembled disk stack on the drum cover, particularly since the disks of the stack of disks also have a preferably conical construction.
According to an embodiment of the present invention, a clear-phase collecting pipe is situated at a lower diameter than the exterior wall of the screw body.
The screw disk, located between the first screw spiral, as viewed from the drum cover, and the drum coverhas a disk-type interior section and a conical exterior section. The maximal radial dimension of the screw disk is smaller than the radial dimension of the screw blade. The conical section of the screw disk as well as the conical drum cover constructed opposite the conical section of the screw disk thereby form the solid matter or concentrate collecting space which is conically tapered twice and which permits a draining of the concentrate toward the drum casing by a removal device at the first screw blade which penetrates the screw disk.
The invention will be better understood and appreciated from the following detailed descriptions and with reference to the accompanying drawings.